We present the first X-PEEM spectromicroscopy semi-quantitative data, acquired on Gd in glioblastoma cell cultures from human brain cancer. The cells were treated with a Gd compound for the optimization of GdNCT (Gadolinium Neutron Capture Therapy). We analyzed the kinetics of Gd uptake as a function of exposure time, and verified that a quantitative analytical technique gives the same results as our MEPHISTO X-PEEM, demonstrating the feasibility of semi-quantitative spectromicroscopy.